Samuel w



July 20,1926. Re. 16,381

' 5- W. CARTER PROPELLER- Original il 1 2. 1922 2 Sheets-Sheet 1 o mm 00 an EA r Q Mm a a Q M 2% a a? v July 20,192

5. w. CARTER Original Filed Oct. 2, 1922 2 Sheets-Sheet 2 BY/ 7 I ATTORNEY M W ma m w m a Reiimed July 20-, 1926.

UNITED STATES mm W. CARTER, WASHINGTON, DISTRICT 0! COLUMBIA.

raoramn.

Original Io. 1,471,590, dated October 28, 1928, Serial Io, 581,927, fled October 2, 1822. Application for reissue filed larch 28, 1926. Serial No. 96,890.

This invention relates to propellers and has special reference to the design and construction of propeller blades.

More particularly the invention relates to 0 an improved method of designing propeller blades and tea blade constructed in accordance'with such method. I

Heretofore it has not been considered that there was any particular relation between the points on the leading edge of the Blade furthest from the horizontal line passing through the center of the hub in the elevational aspectof the blade and the similar points on the trailing edge.

I have discovered that, in order to obtain a maximum efliciency, a certain very definite relation exists between these points. Furthermore, I have discovered that a certain very definite relation exists in the location in distance from the center of the hub to these points and that whenever such relationships are departed from to any material extent thereis a. corresponding ,loss of. efliciency in the propeller. The reason for this is that, when proper cambers are given to the inner and outer portions of the blade a fluid stream will travel from the tip of the blade-towards the hub and another stream will travel from the hubtoward the tip. Now, if the points in question are in proper relationship these two opposing fluid streams will operate to produce a vortex circle or cyclone action, at their junction so that rearward flow of the two streams tends to be obtained without dispersion, and thus the reaction on the propeller blade becomes very great whereby the propulsive efi'ect is greatly enhanced.

One important object of the present in- 40 vention is to 'furnish a key for and to provide a standard method of laying out a propellerblade whereby to determine the location of these points or abices on the leading and trailing edges of the blades in their proper'relation to the center of the hub and to each other. 4 A second very important object of the invention is the provision of a propeller blade so constructed that the apiees of the leading and trailing edges will bear definite relation to each other and to the center of the the center of the hub to the tip of the blade.

I have discovered that a more highly efiicient propeller is produced when the locus of the concentration center or center of thrust is traced by the path of the forty-. eighth radial point, the center of thrust being thus moved inwardly from its usual relation to the tip of the blade and the rear- Wardlyextending fluid current from the blade of the propeller takes the form of a compressed or condensed vortex circle located at a certain distance from the axis of rotation of the propeller. The advantage of this lies principally in the -fact that the stresses are removed from the tip portion of the blade where it is thinnest and the. reaction is concen'tratedin the strong portion of the blade, and the fluid stream set up by the blade does not tend to disperse.

This action is obtained by properly arranging the camber-s of the inner and outer portions of the blades and designing the propeller, in a manner hereinafter described, so that certain relationships exist between the cooperative points on t e leading and trailing edges.

A third important object of the invention is to provide a method of design wherein the proper condensing features of this vortex circle may be obtained.

A fourth important object of the invention is to provide a propeller so constructed that the air or other fluid will have a slip alongthe blade from the center or axis of rotation outward with relation to the inner portion of the blade and inward from the {)ilpdwith' relation to the outer portion of the a e. With the above and other objects in view as will be hereinafter apparent, the invention consists in general of certain novel details of construction and combinations of parts, hereinafter fully described, illustrated in the accompanyingdrawings and specifically claimed.

In the accompanying drawings like characters of reference indicate like partsin the several views. and

Figure '1 is a layout of cross sections of a propeller blade constructed in accordance with this invention and showing the manner of changing from constantpitch used herein. Figure 2 is a face elevation of' one half of a propeller constructed in accordance herewith.

Figure 3 is a plan view of such a half propeller and showing the flow of air currents.

Figure 4 is a diagrammatic face view showing the travel of the centerof thrust, vortex circle, and the main cooperating points on'the leading and trailing edges about the axis of the propeller.

Figure 5 is a diagram to the same scale as Figures 1 and 2, the diagram showing the manner of getting the tip dimensions.

In laying out a propeller blade constructed in accordance with my invention certain features are calculated in the ordinary manner. These features are based on the horsepower of the engine, the number of revolutions per minute of the propeller shaft and the speed desired to be obtained From these factors the proper pitch angle at a certain-distance from the center of the propeller and which I preferably term the key pitch angle can be determined as can also the proper chord width of the propeller blade at the key pitch angle point and the diameter of such propeller, that is to say the diameter of the circle swept by the extreme tip points of the blade.

Having determined by calculation the chord distance and the key pitch angle, the next step is to determine the width of the tip of the blade. To do this a suitable line is drawn of indefinite length as for instance the line a--?) of Figure 5. From a point on this line a line ce is laid off at an angle a: corresponding to the key pitch angle, t e line ce being made equal in length to the chord width of the \blade as calculated.-

The angular line 0-0 is now projected on the line a-b, the projected line being shown at cd and this projected line is divided determined. This leaves a remaining distance fg which is divided into a suitable .number of equal parts preferably seven as indicated at the points g g g g, g", g and Through the point is drawn a chord line h-i which is'prolonged until it intersects the line 10-1l as at the point C. This point is the center or the layout of the primary chord lines of all the blade cross sections. On the line hz' is laid out-the calculated chord width, which is divided into nine equal parts, four-ninths of this width being above the line 12-13 and the remaining tive-ninths bein' below the line 1213. Through the points g 9 g, 9 g and f are drawn other chord lines, and these chord lines at the point 9 and g are represented by the lines iii-4 and at the remaining points by the lines mn. The propeller facc,'and back cambers are deter mined by calculation in the usual manner, and the primary cross sections are completed as in Figure 1, it being noted that all of the primary chord lines may be prolonged to pass through point C. Thus these primary chord lines, if adhered to, would give a blade of uniform pitch, but forthe purpose of this invention this pitch is progressively varied from the cross section at g to cross sectionat f and this variation is accomplished as follows:

From the point i a line is drawn to the point it of the cross section at f, this line being shown as the dotted line z''n. Each of the blade cross sections at the points 9", g and g" is then swung about their respective points m until the point n of that cross section strikes the dotted line the final cross sections being indicated by the dotted lines at the stations 9 g and 9 We now have a complete set of cross sections for the blade, and it will be noted that the chord at 'the station g is nearly equal in length to since the main part of the thrust curves in and is compressed in this neighborhood. The chord at the station g 'is' slightly more than three-fourths of the chord width at the station g, while the chord at the station g is one-half of the sum of the chords at the stations 9 and f, the latter being onehalf of the key chord width hi at the station 9 Moreover, the chords at the stations g,'g g and f are all disposed in their primary positions with four-ninths of the chord width above the line 12-43 and five-ninths below the line 1213 exactly as with the key chord. At the station 7 these proportions change ioabout eleveni .ientythirds above and twelve-twentythirds said lin the chord width be ng varied somewhat to suit the hub dimensions.

It is to be noted that the surface 15 of the ,face of the blade in the lower half of the blade or area between the stations g3 andf as a top line and the straight line in as a bottom line is a plane surface.

s 7 To obtain a'view of the blade in its elevational aspect as shown in Figure 2'we again draw the line 1011 and horizontal line 1213, and at a point 0 which is one-third of the distance from the intersection or cen ter of the hub 14 of the propeller to the tip of the blade 13, a perpendicular op is erected on theline 1213. The distance g h is then projected on the lines 1213 of Figure 1 as at g h and the line line po-p is made equal in length to the distance -72 From the oint -p a is drawn which Is inclined toward t e tip of the blade and intersects the line 1213 at sixty degrees. At the point of the intersection r a line 1' s is drawn perpendicular to 12-13 and this line is made equal in length to the projection of the line g -z' on the line 12 13 or in other words to'zg'i from the point a, a

- horizontal line ag is drawn intermcting the line pg. These points 9 and p are the apex points of the leadin and trailing edges 16 and 17 respectively 0 the propeller blade. The remaining chords of the cross sections in Figure 1 are now'projected on the line 1213 and are laid off on lines projecting through the station points in Figure 2 corresponding to those in Figure 1, per en-.v

dicular lines to the line l213 being aid out at these points. Due to the fact cross sections from the station 9 to the station f decrease in chord regularly the leading and trailing edges 17 and 16 between these cross section stations will be straight lines fairing into the tip curve and the tip of the blade will be a semi-circle havin a ra: dius ef. It will be understood t at by reason of the chord width the station 9 being nearly equal to thechord width at station g the elevational aspect'of this part of the propeller will be almost a rectangle with slightly curved lines at the leading and trailing edges, said curves near the hub eing faired into the hub as shown in this Figure 2.

The plan view (Fig. 3) of the propeller is obtained in a similar manner, the lines 1011 and 1213 being drawn and the station points being laid out as in the other Figure 2. The leading and trailing edges are as indicated at 16 and 17 and in this view it will be noted that the course of the air width is about one and,

currents is such that slip will take place from the hub outwardly and from the t1 inwardl so that a vortex will be forme substantially at the forty-eighth radial point from the hub.

.liith reference to the points [I and q experience has shown that while a certain variation may be allowed in the proportionate distance of the points '0;; the angle of the line p-g must be closely adhered to and the distance in elevational'as ects from the line 1213 must be also close y-adhered to in order to obtain the maximum efficiency \Vith relation to the cambers shown it will be obvious that these cambers are designed in a manner based on the old and well known principles and vary inaccordance with the the elevation at corres onding points in the 1 same proportions as t e maximum widths, that is to say, in the roportions of to 3- of the res ective widtiis. I

It will e observed that the displacement of the points on the leading edge outwardly from the center with respect to the corresponding points on the trailing edge can be mathematically calculated as the displacement in any case is equal to four-ninths of the width at the point multiplied by the tangent of the selected angle preferably the tangent of 60 degrees, for example, if the width at the points be four inches the displacement of the point along the leading edge will be 1.73 x 4 inches, or 6.92.

By this method it is possible to quickly lay out the proper points and when these points are so laid the propeller constructed in accordance therewith is of'very high efliciency, tests having shown an efliciency of 95%.

By reference to Figure 4 is will be seen that the points p and 9 travel in circular Orbits P P, P, P and q a, 9, 9 p

tively and, 38103.11 be seen by the various arrow heads on the circles drawn through these points so that the resultant action of the blade is to produce a helical thrust stream having vortical motion.

edges of the blade by determining the length Having thus described the invention, whatis claimed as new, is:

1. That method of determining the apex I .a predetermined number of said. parts-to determine the apex point of the curve ofthe trailing edge of the blade, laying oil a line from said apex point inclined at a predetermined angle to the horizontal center line and crossing the same, measuring the remainder of the width downward from said horizontal center line perpendicularly thereto to determine the distance from said horizontal center line of the apex point of the leading edge and laying off a line at such distance through the angular line to determine by the intersection of said lines said apex point.

2. That method of determining the apex points of the leading and trailing edges of propeller blades which consists in determining the required length and maximum width of the blade in elevation, describing the vertical and horizontal center lines of the propeller, erecting a perpendicular on the horizontal center line one-third the length' of the blade from the vertical center-line. laying off a point on the perpendicular'at a distance equal to four-ninths the said width from the horizontal center line, the' point thus determined being the apex point of the trailing edges, laying ofi a line through said point and extending outwardly and crossing the horizontal center line at an angle of sixty degrees, and detel-mining a point on said line five-ninths of said width below the horizontal center line to constitute the apex point of the leading ed f'lhat method of laying out propeller blades which consists in determining the apex points ofthe leading and trailing and maximum width in elevation of the desired blade, describing the vertical and horizontal center lines of the elevation of the'propelle'r, erecting a perpendicular at a' point on the horizontal center line a predetermined distance from the vertical center line, dividing-the predetermined width into a number of equal fractional parts, laying off on the perpendicular a predetermined number of said parts to determine the apex point of the curve of the trailing edge of the blade, laying ofl' a line from sai apex point inclined at a predetermined angle to the horizontal center line and crossing the same, measuring the remainder of the width downward from said horizontal center line perpendicularly thereto to determine the distance from said horizontal center line of the apex point of the leading edge, laying oflf a line at such distance through the angular line to determine by the intersection of said lines, said apex points determining the widths in elevation of the blade at a number of other points in its length, laying off, and dividing each of said widths into the same number of fractional parts as the first mentioned width, utilizing a number of the fractional parts of each width equal in number to the fractional 'part of the maximum width used in determining the respective apex points to determine points on the respective edges opposite thepoints at which the last mentioned widths are determined.

4. That method of laying out propeller blades which consists in determining the apex points of the leadin and trailing edges of the blade by determining the required length and maximum width of the blade in elevation, describing the vertical and horizontal center lines of the propeller, erecting a point on said angular line distant perpen dicularly five-ninths of said width from the horizontal center line, said last point being the apexpoint of the leading edge, determining the widths in elevation of theblade at a number of points in its length, la ing off at each of said points four-ninths o the respective width to determine trailing edge points and five-ninths of said width to determine leading edge points.

5. A propeller blade having the apex point of its trailing edge at a predetermined distance from the center of rotation of the being that between said line and-the centerline.

6. A propeller blade having the apexpoint of its trailing edge located'at a disof the leading edge located further from the center by a distance equal to a predetermined fraction of the greatest width of the blade in elevation multiplied by the tangent of sixty de- 7. propeller blade having the apex int of its trailing edge at a predetermined istance from the center of rotation of the propeller and the apex point of its leading edge located further from the center by an amount approximately equal to a predetermined fraction of the atest width of the blade in elevation multiplied b the tangent of a, redetermined angle, sai angle being that tween a line assin through the point on. the trailiritg1 e gean the center line of the blade in p etermined angular relation. to said center line, said apex point of the leading ed mined fractiona part of the maximum width propeller on one side of the center line of the blade in elev'ational exact and the apex point of thet railing edge ing located the remainder of the greatest elevatiofial width on the other side of said line.

.8. A propeller blade having the point of its trailing ed tance from the center the propellerequal to one-third the distance from said center i of a predetermined ang to the tip of the blade and the apex point of its leading edge located further from the center.by a distance equal to the greatest Eidth of the lilade in delevation ,ntiiultiplied by5 etangento sixt e s, sai apex pom of the trailing ed bz ing located at ithe maximum widt of the'blade in elevation from the horizontal center line of the blade in elevational aspect and the apex point of the leading edge'being located of said maximum width on the other side 0 said center line. p 9. A propeller blade having the apex point of its trailing edge at a predetermined distance 1013 itlllie center of rotfationl ofdthe ro eran eapexpointo its ea ing dge l i icated further from'the center by an amount approximately equal to a predeter mined fraction oi the atest widthof the blade in elevation multi lied b the tangent e, sai angle belpg that between a line passing through the point on the trailing ed and the center line of the blade in pre etermined angular relation to said center line, said apex point of the leading edge being located a wpredetermined fractional part of the inaximum width of the propeller on one side of the center line of the blade in elevational ast and the apex point oi the trailing edge ing located the remainder of the greatest elevational width on the other side of said 9 line, the remaining points on said leading being located in predetera ex located at a disand trailing edges being located in corresponding pairs at distances on opposite sides of said center line proportionate to the dispoint of.1ts trailing edge located ata distance from the center of the propeller equal to one-third the distance from said center to the tip of the blade and the apex point of its leading edge located further from the center b width 0 the blade in elevation mu tiplied by the tangent of sixty de ees, said a ex point of the trailin ed e ein locate at i the maximum wi th 0 the b ade in elevation from the horizontal center line of the blade: i? gleqatigiial aspect) and 1the a ex pom 0 to ea' ege ei ocate of said maximum v i'i dth on the ther side 0% said center line, the remaining points on said leading and trailing edges being located in corresponding pairs at distances on opposite sides of said center line proportionate to the distances of the apex points.

11. A propeller blade including an inner' and an outer portion, said inner portion be ng cambered to cause slip of the fluid on whichthe blade acts in an outward direction and the outer portion being shaped to cause slip inwardly of the blade of said fluid, said blade being further shaped to a distance equal to the reatest produce a vortex at the junction of said in- I ner and outer blade portions.

12. A propeller blade includin an inner and an oute:' portion, said inner lower portion being cambered to cause slip of the fluid on which the blade acts in an outward direction and the 'outer portion being shaped to cause slip inwardly of the blade of said fluid, said inner and outer rtions being respectively and the ength of the blade.

13. A propeller blade having an angle of attack greater than 45 de ees adjacent its inner end and an angle 0 attack less, than 45 degrees at its outer end, the angle of attack va 'ng rog'ressively from one end of the bla e to t e other whereby the angle of attack at one point equals 45 degrees said blade having the outer portion beyon the said point' shaped to direct a fluid stream inwardl along the blade and havin the inner portion shaped to direct a flui stream outwardly along the blade whereby said streams meet at approximately said point.

14. A propeller blade having an angle of attack greater than 45 de rees adjacent its inner end and an angle 0% attack less than 45 degrees at its outer end, the angle of attack varying progressively from one end of the blade to the other whereby the angle of attack at one point equals 45 degrees, said bladehaving the'outer poition beyond the said point shaped to direct a fluid stream inpitch cross sections, t e leading edge of theof the trailing on its traili secon streams meet at approximately said int, said inner and outer blade portions ing f a flui further she to cause formation 0 vortex at streams.

15. A pro in its 1 e point of meeting of the fluid er blade having atone point and ad'acent its tip constant lade between such ores pectiona bemga straight line, the cross sections between sa d cross sections having contours identical m form and dimensions with constant pitch cross sections at the points at which they are taken,.-each of said cross sections being positioned in such angular dis lacement about the cross section point on t e trailing as'to bring the cross section int on leadin edge on said straight line.

16. ro ller blade portion 0 t e blade of uniform itch and the outer portion of the blade 'o vary ng pitch, the pitch oi the inner rtion be ng such as to force air outwar y along the blade and the varying pitch of the outer gortion being such as to force a1r 1nwardly and the outer rtion being of gradually va pitch t e face of the outer portionof tl bl ade adjacent the leading edge'being a plane surface.

18, A propeller blade having on its leading edge an apex point or point of eatest distance from the center line of the lade in elevational aspect and a similar apex point ed the apex pomt on its leadin edge ing more remote from the axis 0 the propeller than the apexpolnt of 'the trailing edge whereby the orbit of the first int, is greater than the-orbit of the second int and said points revolve around each otb r as the re eller revolves.

19. A propeller la e having on its leading an apex point or point of reatest distance from the center line of the lads in elevational aspect, and a similar apex point on its trailingmedge, the apex po1nt on its leading e in more, remote from the axis 0 the pro er than the apex point edge whereby the orbit of the int is greater than the orbit of the each 0 er as th propeller revolves, said blade being of varying pitchfiin its outer aving the innerm the tiptoward the center of the pro int and said points revolve around use? part to produce inward flow of the air from the tip of the blade toward the'first oint, V

and cambered to produce the outwar 'flow of the air from the hub toward the second point. 7

20. A propeller blade having on its leading edge an apex point or point of greatest distance from the center line of the blade in elevational aspect, and a similar apex point on its trailing edge, the apex point on its leadin edge being more remotefrom the o the. p ller than the apex point of the trailing e whereby the orbit of the first int is greater-than the orbit of the secon oint and said points revolve around each at er as the pro eller revolves, said second point being atsu stantially one-third the distance from the hub to the tip of the propeller.

21. A propeller blade having on its leading edge an apex point or point of greatest distance from the center line of the blade in elevational aspect and a; similar apex point on its trailin ed the apex point on its leadin edge ing more remote from the axis 0 the propeller than the apex point of the trailing edge whereby the orbit of the first point is greater than the orbit of the second oint and 'said points revolve around each ot eras the pro eller revolves, said second point being at su stantially one-third elevational aspect, and a similar apex point on its trailin edge, the apex point on its leading edge eing more remote from the axis of the propeller than the apex point of the trailing edge whereby the orbit of the first goint is greater-than the orbit of the secon point and said points revolve around each other as the propeller revolves, said second oint being at substantially one-third the istance 'from the hub to the tip of the propeller, the first point being on a hne drawn at 60 degrees to the center line of the blade and passing through the second point.- I

23. A propeller blade having on its leading ed'ge anapex point or point of greatest distance from the center line of.the blade in' elevational aspect and a similar a point on its trailin edge, the apex point on its leadin edge eing more remote from the axis 0 the propeller than the apex point of the trailing edge whereby the orbit of the first point is greater thanthe' orbit of the second point and said points revolve around rope? each other as the pro ller revolves, said from the tip of the blade toward the first second point being at surstantially one-"third int, and cambered to produce the outward 10 the distance from the hub to the tip of the ow of the air from the hub toward the sec- Err-opener; the first point being on a line 0nd point. a

P wn at 60' degrees to the center line ofthe In witness whereof I hereunto aflix my blade and p through the second point, signature. said blade being of varying pitch 1n its r d outer part to produce inward flow of air SAMUELVV. CARTER. 

